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I have dual boot of Win8.1 and Ubuntu 14.04. I tried to recover my write protected pendrive with diskmgr on win cmd. I failed and now can't start pc on win or ubuntu. A black screen coming before boot or grub menu come. The Black screen containing nothing but a _ (underscore). Please help. Here is image links to be clear

And here is the current status.

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For a proper diagnosis, more information is needed: Boot an emergency Linux disc (like the installer in its "try before installing" mode) and run the Boot Info Script. This will produce a file called RESULTS.txt with lots of output. Post it to a pastebin site and post the URL to your document here.

Without a proper diagnosis, there are two shot-in-the-dark approaches that might get you up and running again:

  • Download the USB flash drive or CD-R version of my rEFInd boot manager and prepare a medium from the image. Disable Secure Boot (if it's active) and boot the medium. It should give you options to boot both Windows and Ubuntu. If both options work, boot to Ubuntu and install the Debian-package version of rEFInd. It should then take over your boot manager duties.
  • Boot to Linux (using either an emergency disk in EFI mode or rEFInd to boot the Linux on your hard disk) and run the Boot Repair tool. This program will re-install GRUB on your hard disk, which should begin working again.

Note that the Boot Repair approach involves more of a leap of faith than the rEFInd approach. With rEFInd, the USB drive or CD-R boot serves as a proof of concept; if you can boot from the USB drive, you can be certain that rEFInd will work if the install to the hard disk is successful. With Boot Repair, though, there's no way to test its installation before it's done. In your case, it is at least unlikely to do any further damage.

If both methods fail, post the URL that Boot Repair produces. This is essentially the same output that Boot Info Script produces.

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Thanks Rod for your replay. I used ubuntu live cd to solve my problem but as an ubuntu newbie I wasn't succeed. I also tried it with windows recovery command prompt but it said the partitions were locked and I activated them. (My bad luck) I wasn't solved then. After all I installed ubuntu on my desktop again and its working great again. My all partitions are fine. – pappox Aug 4 '14 at 15:24

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